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The employee ran bitcoin-mining software on the computer every night from 6 p.m. to 6 a.m. for an entire month in 2014.

A computer-systems manager at New York City’s Department of Education has been fined for using his work computer to mine bitcoins, the city’s Conflicts of Interest Board announced Monday.

The employee, Vladimir Ilyayev, ran bitcoin-mining software on the computer every night from 6 p.m. to 6 a.m. for an entire month in 2014, according to the announcement.

“During that time, I monitored the progress of my bitcoin mining software from my home computer using remote access software,” Ilyayev said in a disposition, also released Monday.

He has now agreed to “forfeit four days of annual leave, valued at approximately $611,” the agency said.

The process of bitcoin mining involves running a program that contributes to building the blockchain—the currency’s transactional infrastructure—by solving complex math problems, and receiving rewards in the form of fees. It takes a lot of time and processing power to actually make any money from bitcoin mining, however, and the deposition did not specify whether the employee was successful.

In the disposition, Ilyayev said he was thwarted in his attempts to install the necessary software five or six times before circumventing the department’s security system.